Swing Vote (PG-13) **

Politics aside, this Bud's for you.

It's tempting to say that the election-day shenanigans in Swing Vote are too preposterous to happen, but I live in Florida, so perhaps it's best in this case to never say never.

Reality is beside the point, anyway. Swing Vote aims to be a Capra-esque fantasy in which that old adage about every vote counting is true, even if that man is an ignorant trailer-park slob who knows nothing about politics, can't keep a job and spends more time nursing a Budweiser than nurturing his young daughter.

Kevin Costner plays the aptly named Bud, and he's having such a good time as this affable loser that he distracts you from the plot's more trying developments. Bud, his Bass Pro Shops cap never far from his unkempt head, isn't even registered to vote -- like many nervous citizens, he fears jury duty -- but his precocious daughter Molly (Madeline Carroll) registers him and even tries to cast his vote when he's too drunk to make it to the polling precinct. Technical problems ensue, and Bud is offered a second chance to vote. Meanwhile, the presidential election hinges on his decision.

Costner wears his disheveled role so engagingly he almost makes up for the fact that Molly is supremely annoying. (She says that when she grows up she wants to be a veterinarian or chairman of the Fed.) Her sourpuss reaction as Bud giggles his way through the desperate overtures of the Republican president (an excellent Kelsey Grammer) and his Democratic challenger (Dennis Hopper) makes you wish Bud had packed her off to the appropriate child-care agency long ago. She may be mad at her clueless, good-timing dad, but she's smart enough to know voter fraud is a felony, so why is she mad at Bud, who's trying to save her bacon?

The film eventually bogs down in drama, with an unnecessary subplot involving Bud's estranged wife and an ethical dilemma for a local news reporter (Paula Patton) that never really gets off the ground. The most inspired bits are the candidates' rapidly deteriorating ads, aimed only at Bud, as the conniving campaign managers (Stanley Tucci and Nathan Lane) struggle to decipher what he wants to hear. His careless ''Who doesn't like life?'' comment leads to a horrifyingly inappropriate anti-abortion ad from the Democrats, a hilarious new low in pandering.

Everyone, including the candidates, will recognize the importance of civic duty, leaving Swing Vote to end with swelling music and uplifting speechifying but on a completely unsatisfactory note. As pushy little Molly will tell you: You've got to pick a side to make a difference.